Patients with early-stage MMR-deficient CRC do not appear to benefit from adjuvant 5-Fluorouracil monotherapy (Ribic et al., 2003); however, in some patients with metastatic MMR-deficient CRC, treatment with immune checkpoint inhibitors has been associated with an excellent response (Le et al., 2017). This evidence concerns the gene MRC1 and colorectal carcinoma.